The present invention relates to a transfer printing method wherein with utilization of a thermal transfer technique a master image containing a sublimation dye is formed, and then the sublimation dye in the master image is transferred onto an image receptor such as textile goods to form a dyed image thereon.
There is a transfer printing method using a sublimation dye as one of the methods of forming dyed images on textile goods. According to this method, generally, a transfer paper sheet wherein an image is printed on a sheet of paper with a printing ink containing a sublimation dye is formed first, then pressed against a textile article, followed by heating to give a dyed image thereon. Such a method, however, needs to fabricate a form for forming the transfer paper sheet and is, hence, suitable for mass production but unsuitable for production of diversified items each in an small amount.
On the other hand, there is a method of the type wherein with use of a thermal transfer ink sheet provided on a foundation with a non-transferable resin layer containing a sublimation dye, an image is printed on an image receptor such as a paper sheet with a thermal transfer printer. Such a method will be referred to as "direct transfer method" hereinafter. This method, although suitable for production of diversified items each in a small amount, has a difficulty in obtaining a clear dyed image if an image receptor is of textile because the heating energy produced by a thermal head of a typical thermal transfer printer is not so large.
As a method which overcomes the drawbacks of the above two method wherein with use of a thermal transfer ink sheet provided on a foundation with a heat-meltable ink layer containing a sublimation dye, the ink layer is selectively melt-transferred onto a master sheet such as made of paper with a thermal transfer printer to form a master having an image of heat-meltable ink containing the sublimation dye, and then this master is pressed against a textile article and heated to cause the sublimation dye therein to transfer onto the textile article, thereby obtaining a dyed image (refer to Japanese Unexamined Patent Publication No. 102390/1982). With such a method a dyed image of a desired design can be readily obtained as compared with the foregoing transfer printing method since a master can be formed with a thermal transfer printer, and a clearer dyed image can be obtained on a textile article as compared with one obtained by the foregoing direct transfer method since the transfer from the master can be achieved with a hot press or the like.
With the transfer printing method disclosed in the above publication, however, merely a monochromatic dyed image is obtained from a single master. Recently, there has been a strong desire to obtain a polychromatic dyed image from a single master in accordance with this transfer printing method.
An attempt has been made by the present inventors to obtaining a polychromatic image from a single master by using a thermal transfer ink sheet wherein applied on a foundation are a heat-meltable ink Y containing an yellow sublimation dye, heat-meltable ink M containing a magenta sublimation dye and heat-meltable ink C containing a cyan sublimation dye, sequentially selective-transferring these inks onto a master sheet to form a master image in which the inks are superimposed one on the other, and pressing this master image against a textile article while heating to cause the sublimation dyes in the master image to transfer onto the textile article.
By the way, a thermal transfer color printer which is commercially available at present uses a thermal transfer ink sheet wherein on a single foundation or a plurality of foundations are applied a heat-meltable transparent ink layer Y containing an yellow pigment, heat-meltable transparent ink layer M containing a magenta pigment and heat-meltable transparent ink layer C containing a cyan pigment, and is adapted to form a polychromatic image in accordance with the subtractive color mixture of yellow, magenta and cyan by sequentially transferring these transparent inks onto an image receptor such as made of paper to form a printed image in which the transparent inks for respective colors are superimposed one on the other. With this printer, for example, red is obtained by superimposing the yellow and magenta inks on each other, green by the yellow and cyan inks, blue by the magenta and cyan inks, and black by the yellow, magenta and cyan inks.
It is known that in obtaining a color other than the three primary colors by superimposing transparent inks of the primary colors the color reproducibility depends on the order of superimposition, and that the superimposition of yellow, magenta and cyan ink layers in this order from an image receptor offers the best color reproducibility. For this reason the thermal transfer color printer is designed to transfer the inks for respective colors in that order.
Accordingly, in the case of the thermal transfer ink sheet provided on a single foundation with the transparent inks for respective colors, the yellow ink Y, magenta ink M and cyan ink C are arranged in the order of Y, M and C in the direction opposite to the ribbon-feeding direction (indicated by an arrow) as shown in FIG. 9. The arrangement of Y, M and C constitutes a pattern P which is repeatedly provided on the foundation. Correspondingly the thermal transfer color printer is designed to transfer the inks for respective colors in the order of Y.fwdarw.M.fwdarw.C (which means that Y is transferred first, M second and C third).
If the thermal transfer color printer is employed to form the aforesaid master for transfer printing, the inks respectively containing sublimation dyes in the thermal transfer ink sheet for forming the master are arranged in the same order as in the thermal transfer ink sheet for superimposing transparent inks, and transferred in the order of Y.fwdarw.M.fwdarw.C. In the master image formed in this manner, Y, M and C are superimposed in this order on the master sheet.
However, it has been found that transfer printing on a textile article with use of such a master cannot offer a satisfactory color reproducibility.
It is an object of the present invention to improve the color reproducibility offered by a transfer printing method wherein a master is formed by superimposing inks containing sublimation dyes for respective colors by means of thermal transfer and a polychromatic dyed image is obtained by transferring the sublimation dyes from the master onto a textile article.
This and other object will become apparent from the description hereinafter.